The use of colored lights as indicators in monitoring systems is well known. These lights, however, are generally an incandescent lamp of a single color and can be used to indicate two conditions at most. Red lights, for example, are commonly used to indicate danger or malfunction, and are generally connected so that absence of a light indicates the system is functioning normally and the presence of the light indicates a failure of the system.
This has the obvious disadvantage of requiring a separate light for each element of the system monitored. This can result in a confusing array of lights where many functions of a complicated system must be monitored.
It would be advantageous to have a single indicator light capable of indicating the condition of many separate elements of a system. It would also be advantageous to have a single light capable of generating any color of the spectrum.